javax.management.loading
Class MLet

java.lang.Object
  |
  +--java.lang.ClassLoader
        |
        +--java.security.SecureClassLoader
              |
              +--java.net.URLClassLoader
                    |
                    +--javax.management.loading.MLet
All Implemented Interfaces:
MBeanRegistration, MLetMBean

public class MLet
extends java.net.URLClassLoader
implements MLetMBean, MBeanRegistration

Allows you to instantiate and register one or several MBeans in the MBean server coming from a remote URL. M-let is a shortcut for management applet. The m-let service does this by loading an m-let text file, which specifies information on the MBeans to be obtained. The information on each MBean is specified in a single instance of a tag, called the MLET tag. The location of the m-let text file is specified by a URL

The MLET tag has the following syntax:

  
 	  [arglist]
  
 

Where:

CODE = class
This attribute specifies the full Java class name, including package name, of the MBean to be obtained. The compiled .class file of the MBean must be contained in one of the .jar files specified by the ARCHIVE attribute. Either CODE or OBJECT must be present.

OBJECT = serfile
This attribute specifies the .ser file that contains a serialized representation of the MBean to be obtained. This file must be contained in one of the .jar files specified by the ARCHIVE attribute. If the .jar file contains a directory hierarchy, specify the path of the file within this hierarchy. Otherwise a match will not be found. Either CODE or OBJECT must be present.

ARCHIVE = "archiveList"
This mandatory attribute specifies one or more .jar files containing MBeans or other resources used by the MBean to be obtained. One of the .jar files must contain the file specified by the CODE or OBJECT attribute. If archivelist contains more than one file:

All .jar files in archivelist must be stored in the directory specified by the code base URL.

CODEBASE = codebaseURL
This optional attribute specifies the code base URL of the MBean to be obtained. It identifies the directory that contains the .jar files specified by the ARCHIVE attribute. Specify this attribute only if the .jar files are not in the same directory as the m-let text file. If this attribute is not specified, the base URL of the m-let text file is used.

NAME = mbeanname
This optional attribute specifies the object name to be assigned to the MBean instance when the m-let service registers it. If mbeanname starts with the colon character (:), the domain part of the object name is the domain of the agent. The m-let service invokes the getDomain() method of the Framework class to obtain this information.

VERSION = version
This optional attribute specifies the version number of the MBean and associated .jar files to be obtained. This version number can be used to specify that the .jar files are loaded from the server to update those stored locally in the cache the next time the m-let text file is loaded. version must be a series of non-negative decimal integers each separated by a period from the one that precedes it.

arglist
This optional attribute specifies a list of one or more parameters for the MBean to be instantiated. This list describes the parameters to be passed the MBean's constructor. Use the following syntax to specify each item in arglist:

                      
 
where: The arguments' type in the argument list should be a Java primitive type or a Java basic type (java.lang.Boolean, java.lang.Byte, java.lang.Short, java.lang.Long, java.lang.Integer, java.lang.Float, java.lang.Double, java.lang.String).

When an m-let text file is loaded, an instance of each MBean specified in the file is created and registered

The m-let Service extends the java.net.URLClassLoader and can be used to load remote classes and jar files in the VM of the agent

Note - The MLet class loader uses the @see javax.management.MBeanServerFactory#getClassLoaderRepository to load classes that could not be found in the loaded jar files.


Constructor Summary
MLet()
          Constructs a new MLet using the default delegation parent ClassLoader
MLet(java.net.URL[] urls)
          Constructs a new MLet for the specified URLs using the default delegation parent ClassLoader.
MLet(java.net.URL[] urls, java.lang.ClassLoader parent)
          Constructs a new MLet for the given URLs.
MLet(java.net.URL[] urls, java.lang.ClassLoader parent, java.net.URLStreamHandlerFactory factory)
          Constructs a new MLet for the specified URLs, parent class loader, and URLStreamHandlerFactory.
 
Method Summary
 void addURL(java.lang.String url)
          Appends the specified URL to the list of URLs to search for classes and resources.
 void addURL(java.net.URL url)
          Appends the specified URL to the list of URLs to search for classes and resources
protected  java.lang.Class findClass(java.lang.String name)
          This is the main method for class loaders to load/find the class
protected  java.lang.String findLibrary(java.lang.String libraryName)
          Returns the absolute path name of a native library.
 java.lang.String getLibraryDirectory()
          Gets the current directory used by the library loader for storing native libraries before they are loaded into memory
 java.util.Set getMBeansFromURL(java.lang.String url)
          Loads a text file containing MLET tags that define the MBeans to be added to the agent.
 java.util.Set getMBeansFromURL(java.net.URL url)
          Loads a text file containing MLET tags that define the MBeans to be added to the agent.
 java.lang.Class loadClass(java.lang.String name, ClassLoaderRepository repository)
          Load a class using the given ClassLoaderRepository, iterating through the list of class loaders.
 void postDeregister()
          Allows the m-let to perform any operations needed after having been de-registered in the MBean server
 void postRegister(java.lang.Boolean registrationDone)
          Allows the m-let to perform any operations needed after having been registered in the MBean server or after the registration has failed.
 void preDeregister()
          Allows the m-let to perform any operations it needs before being de-registered by the MBean server.
 ObjectName preRegister(MBeanServer server, ObjectName name)
          Allows the m-let to perform any operations it needs before being registered in the MBean server.
 void setLibraryDirectory(java.lang.String libdir)
          Sets the directory used by the library loader for storing native libraries before they are loaded into memory
 
Methods inherited from class java.net.URLClassLoader
definePackage, findResource, findResources, getPermissions, getURLs, newInstance, newInstance
 
Methods inherited from class java.security.SecureClassLoader
defineClass
 
Methods inherited from class java.lang.ClassLoader
clearAssertionStatus, defineClass, defineClass, defineClass, definePackage, findLoadedClass, findSystemClass, getPackage, getPackages, getParent, getResource, getResourceAsStream, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, loadClass, resolveClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface javax.management.loading.MLetMBean
getResource, getResourceAsStream, getResources, getURLs
 

Constructor Detail

MLet

public MLet()

Constructs a new MLet using the default delegation parent ClassLoader


MLet

public MLet(java.net.URL[] urls)

Constructs a new MLet for the specified URLs using the default delegation parent ClassLoader. The URLs will be searched in the order specified for classes and resources after first searching in the parent class loader.

Parameters:
urls - - the urls from which to load classes and resources

MLet

public MLet(java.net.URL[] urls,
            java.lang.ClassLoader parent)

Constructs a new MLet for the given URLs. The URLs will be searched in the order specified for classes and resources after first searching in the specified parent class loader. The parent argument will be used as the parent class loader for delegation. The factory argument will be used as the stream handler factory to obtain protocol handlers when creating new URLs.

Parameters:
urls - - the urls from which to load classes and resources
parent - - The parent class loader for delegation.

MLet

public MLet(java.net.URL[] urls,
            java.lang.ClassLoader parent,
            java.net.URLStreamHandlerFactory factory)

Constructs a new MLet for the specified URLs, parent class loader, and URLStreamHandlerFactory. The parent argument will be used as the parent class loader for delegation. The factory argument will be used as the stream handler factory to obtain protocol handlers when creating new URLs.

Parameters:
urls - - the urls from which to load classes and resources
parent - - The parent class loader for delegation.
factory - - The URLStreamHandlerFactory to use when creating URLs
Method Detail

preRegister

public ObjectName preRegister(MBeanServer server,
                              ObjectName name)
                       throws java.lang.Exception

Allows the m-let to perform any operations it needs before being registered in the MBean server. If the ObjectName is null, the m-let provides a default name for its registration :type=MLet

Specified by:
preRegister in interface MBeanRegistration
Parameters:
server - - the MBeanServer in which the MLet will be registered.
name - - the ObjectName of the MLet
Returns:
ObjectName The name of the registered MBean
Throws:
java.lang.Exception - - This exception should be caught by the MBean server and re-thrown as an MBeanRegistrationException.

postRegister

public void postRegister(java.lang.Boolean registrationDone)

Allows the m-let to perform any operations needed after having been registered in the MBean server or after the registration has failed.

Specified by:
postRegister in interface MBeanRegistration
Parameters:
registrationDone - - Indicates whether or not the m-let has been successfully registered in the MBean server. The value false means that either the registration phase has failed.

preDeregister

public void preDeregister()
                   throws java.lang.Exception

Allows the m-let to perform any operations it needs before being de-registered by the MBean server.

Specified by:
preDeregister in interface MBeanRegistration
Throws:
java.lang.Exception - - This exception should be caught by the MBean server and re-thrown as an MBeanRegistrationException

postDeregister

public void postDeregister()

Allows the m-let to perform any operations needed after having been de-registered in the MBean server

Specified by:
postDeregister in interface MBeanRegistration

addURL

public void addURL(java.lang.String url)
            throws ServiceNotFoundException

Appends the specified URL to the list of URLs to search for classes and resources.

Specified by:
addURL in interface MLetMBean
Parameters:
url - - the url represented as a string to add to the list of urls specified
Throws:
- - ServiceNotFoundException if the specified URL is malformed
ServiceNotFoundException

addURL

public void addURL(java.net.URL url)

Appends the specified URL to the list of URLs to search for classes and resources

Specified by:
addURL in interface MLetMBean
Overrides:
addURL in class java.net.URLClassLoader
Parameters:
url - - the url as a URL to be added to the list of urls specifed

loadClass

public java.lang.Class loadClass(java.lang.String name,
                                 ClassLoaderRepository repository)
                          throws java.lang.ClassNotFoundException

Load a class using the given ClassLoaderRepository, iterating through the list of class loaders. The given ClassLoaderRepository can be null, in which case it is equivalent to ClassLoader.loadClass(java.lang.String)

Parameters:
name - - The name of the class we want to load.
repository - - The ClassLoaderRepository that will be used to search for the given class, if it is not found in this ClassLoader
Returns:
- the loaded class object
Throws:
- - ClassNotFoundException if the specified class could not be found, neither in this ClassLoader nor in the given ClassLoaderRepository
java.lang.ClassNotFoundException

findClass

protected java.lang.Class findClass(java.lang.String name)
                             throws java.lang.ClassNotFoundException

This is the main method for class loaders to load/find the class

Overrides:
findClass in class java.net.URLClassLoader
Parameters:
name - - the name of the class to load/find
Throws:
java.lang.ClassNotFoundException - - if the class was not found

getMBeansFromURL

public java.util.Set getMBeansFromURL(java.lang.String url)
                               throws ServiceNotFoundException

Loads a text file containing MLET tags that define the MBeans to be added to the agent. The location of the text file is specified by a URL. The MBeans specified in the MLET file will be instantiated and registered by the MBean server.

Specified by:
getMBeansFromURL in interface MLetMBean
Parameters:
url - - The URL of the text Mlet file to be loaded as String object
Returns:
A set containing one entry per MLET tag in the m-let text file loaded. Each entry specifies either the ObjectInstance for the created MBean, or a throwable object (that is, an error or an exception) if the MBean could not be created.
Throws:
ServiceNotFoundException - - One of the following errors has occurred:
  • The m-let text file does not contain an MLET tag
  • The m-let text file is not found
  • A mandatory attribute of the MLET tag is not specified
  • The url is malformed.
java.lang.IllegalStateException - - MLet MBean is not registered with an MBeanServer

getMBeansFromURL

public java.util.Set getMBeansFromURL(java.net.URL url)
                               throws ServiceNotFoundException

Loads a text file containing MLET tags that define the MBeans to be added to the agent. The location of the text file is specified by a URL. The MBeans specified in the MLET file will be instantiated and registered by the MBean server

Specified by:
getMBeansFromURL in interface MLetMBean
Parameters:
url - - The URL of the file to loaded as a URL
Throws:
java.lang.IllegalStateException - - MLet MBean is not registered with an MBeanServer.
ServiceNotFoundException

findLibrary

protected java.lang.String findLibrary(java.lang.String libraryName)

Returns the absolute path name of a native library. The VM invokes this method to locate the native libraries that belong to classes loaded with this class loader. Libraries are searched in the JAR files using first just the native library name and if not found the native library name together with the architecture-specific path name (OSName/OSArch/OSVersion/lib/nativelibname), i.e.

the library stat on Solaris SPARC 5.7 will be searched in the JAR file as:

  1. libstat.so
  2. SunOS/sparc/5.7/lib/libstat.so

the library stat on Windows NT 4.0 will be searched in the JAR file as:

  1. stat.dll
  2. WindowsNT/x86/4.0/lib/stat.dll
If this method returns null, i.e. the libraries were not found in any of the JAR files loaded with this class loader, the VM searches the library along the path specified as the java.library.path property

Overrides:
findLibrary in class java.lang.ClassLoader
Parameters:
libraryName - - the name of the library
Returns:
the absolute path of the native library

getLibraryDirectory

public java.lang.String getLibraryDirectory()

Gets the current directory used by the library loader for storing native libraries before they are loaded into memory

Specified by:
getLibraryDirectory in interface MLetMBean
Returns:
The current directory used by the library loader

setLibraryDirectory

public void setLibraryDirectory(java.lang.String libdir)

Sets the directory used by the library loader for storing native libraries before they are loaded into memory

Specified by:
setLibraryDirectory in interface MLetMBean
Parameters:
libdir - - the directory the library is stored in.


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